Method for cutting object to be processed

Abstract

The object cutting method comprises the steps of locating a converging point of laser light within a monocrystal sapphire substrate, while using a rear face of the monocrystal sapphire substrate as an entrance surface of the laser light, and relatively moving the converging point from one side to the other side along each of a plurality of lines to cut set parallel to the a-plane and rear face of the substrate, so as to form a modified region within the substrate along each line; and thereafter exerting an external force on the object along each line, so as to extend a fracture occurring from the modified region, thereby cutting the object along each line.

1 . An object cutting method for manufacturing a plurality of light-emitting elements by cutting an object to be processed, comprising a monocrystal sapphire substrate having front and rear faces forming an angle corresponding to an off-angle with c-plane and an element layer including a plurality of light-emitting element parts arranged in a matrix on the front face, with respect to each of the light-emitting element parts, the method comprising:
 a first step of locating a converging point of laser light at a position separated by a first distance from the rear face within the monocrystal sapphire substrate, while using the rear face as an entrance surface of laser light in the monocrystal sapphire substrate, and relatively moving the converging point from one side to the other side along each of a plurality of first lines to cut set parallel to a-plane of the monocrystal sapphire substrate and the rear face, so as to form first modified regions within the monocrystal sapphire substrate along each of the first lines; and   a second step of exerting an external force on the object along each of the first lines after the first step, so as to extend a first fracture occurring from the first modified regions, thereby cutting the object along each of the first lines.   
     
     
         2 . An object cutting method according to  claim 1 , wherein, in the first step, assuming that side where r-plane of the monocrystal sapphire substrate and the rear face form an acute angle is the one side while side where the r-plane and the rear face form an obtuse angle is the other side, the converging point is relatively moved from the one side to the other side along each of the first lines, so as to form the first modified regions within the monocrystal sapphire substrate and cause the first fracture to reach the rear face. 
     
     
         3 . An object cutting method according to  claim 2 , wherein, in the second step, the external force is exerted on the object along each of the first lines by pressing a knife edge against the object from the rear face side along each of the first lines. 
     
     
         4 . An object cutting method according to  claim 1 , further comprising:
 a third step of locating the converging point within the monocrystal sapphire substrate, while using the rear face as the entrance surface, and relatively moving the converging point along each of a plurality of second lines to cut set parallel to m-plane of the monocrystal sapphire substrate and the rear face, so as to form second modified regions within the monocrystal sapphire substrate along each of the second lines before the second step; and   a fourth step of exerting an external force on the object along each of the second lines after the first and third steps, so as to extend a second fracture occurring from the second modified regions, thereby cutting the object along each of the second lines.   
     
     
         5 . An object cutting method according to  claim 1 , wherein, in the first step, the converging point is located at a position separated by a second distance greater than the first distance from the rear face within the monocrystal sapphire substrate, while using the rear face as the entrance surface, and the converging point is relatively moved from the other side to the one side along each of the first lines, so as to form third modified regions within the monocrystal sapphire substrate along each of the first lines; and
 wherein, in the second step, the external force is exerted on the object along each of the first lines, so as to extend the first fracture and a third fracture occurring from the third modified regions, thereby cutting the object along each of the first lines.   
     
     
         6 . An object cutting method according to  claim 1 , wherein, in the first step, the converging point is located at a position separated by a second distance greater than the first distance from the rear face within the monocrystal sapphire substrate, while using the rear face as the entrance surface, and the converging point is relatively moved the converging point from the one side to the other side along each of the first lines, so as to form third modified regions within the monocrystal sapphire substrate along each of the first lines; and
 wherein, in the second step, the external force is exerted on the object along each of the first lines, so as to extend the first fracture and a third fracture occurring from the third modified regions, thereby cutting the object along each of the first lines.